1. Technical Field
The present invention relates to a method for forming a pulsating air pattern at a surface of an electronic carrier assembly.
2. Related Art
An electronic carrier assembly comprises an electronic carrier, such as a circuit board, having an attached electronic component such as a module or a chip. When electric current flows within an electronic carrier assembly, heat is generated and the heat must be dissipated. Natural convection provides an effective mechanism for heat removal where the required rate of heat removal is small. For situations in which the required rate of heat removal is large, a cooling fan is typically used, since a fan generates an air flow across a surface of an electronic carrier assembly which removes heat by forced convection. The heat transfer coefficient associated with forced convection, which is generally higher than the heat transfer coefficient associated with natural convection, increases as the velocity of air flow increases. A surface of an electronic carrier assembly includes the surface of the electronic carrier and the surfaces of electronic components attached to the electronic carrier. Under this definition, a surface of an electronic carrier assembly includes surfaces from which heat may be transferred from the electronic carrier assembly to the surrounding air, or other surrounding fluid.
The required rate of heat removal increases with increasing current flow, which is a consequence of increasing power input. The required rate of heat removal is generally higher in a closed system than in an open system. Under the assumption that the electronic carrier assembly is coupled to a housing, a closed system is a configuration in which one or more housing surfaces are located so as to impede air flow normal to the surfaces of the electronic carrier assembly. With an open system, housing surfaces do not impede air flow normal the surfaces of the electronic carrier assembly. Accordingly, an open system allows better heat transfer from an electronic carrier assembly than does a closed system when the primary mode of heat transfer is natural convection, especially when the electronic carrier assembly is oriented vertically. With forced convection and adequate venting, a closed system is the more efficient system for dissipating heat, because the housing enhances the air flow velocity at the surface of the electronic carrier assembly. A disadvantage of a closed system with forced convection heat transfer, however, is a generation of higher pressure drops, which in turn raises the level of acoustic noise. Another applicable system is a partially open system in which housing surfaces are located so as to impede air flow normal from one surface of the electronic carrier assembly, but not from another surface of the electronic carrier assembly.
While present systems remove heat from operating electronic carrier assemblies, it would be advantageous to remove such heat removal more efficiently. It would also be advantageous to remove heat from an electronic carrier assembly by natural convection where a cooling fan would otherwise be required.